Fos expression at the cerebellum following non-contact arousal and mating behavior in male rats

Current Opinion on the Use of c-Fos in Neuroscience

For years, the biochemical processes that are triggered by harmful and non-harmful stimuli at the central nervous system level have been extensively studied by the scientific community through numerous techniques and animal models. For example, one of these techniques is the use of immediate expression genes, which is a useful, accessible, and reliable method for observing and quantifying cell activation. It has been shown that both the c-fos gene and its protein c-Fos have rapid activation after stimulus, with the length of time that they remain active depending on the type of stimulus and the activation time depending on the stimulus and the structure studied. Fos requires the participation of other genes (such as c-jun) for its expression (during hetero-dimer forming). c-Fos dimerizes with c-Jun protein to form factor AP-1, which promotes the transcription of various genes. The production and removal of c-Fos is part of cellular homeostasis, but its overexpression results in increased cell proliferation. Although Fos has been used as a marker of cellular activity since the 1990s, which molecular mechanism participates in the regulation of the expression of this protein is still unknown because the gene and the protein are not specific to neurons or glial cells. For these reasons, this work has the objective of gathering information about this protein and its use in neuroscience.

Status Epilepticus Increases Cell Proliferation and Neurogenesis in the Developing Rat Cerebellum

Status epilepticus (SE) promotes neuronal proliferation and differentiation in the adult and developing rodent hippocampus. However, the effect of SE on other neurogenic brain regions such as the cerebellum has been less explored. To determine whether SE induced by pentylentetrazole (PTZ-SE) and lithium-pilocarpine (Li-Pilo-SE) increases cell proliferation and neurogenesis in the developing rat cerebellum. SE was induced in 14-day-old (P14) Wistar rat pups (both sexes). One hour after SE and the following day rats were injected intraperitoneally with 5-bromo-2'-deoxyuridine (BrdU, 50 mg/kg). Seven days after SE, immunohistochemistry was performed to detect BrdU-positive (BrdU+) cells or BrdU/NeuN+ cells in the cerebellar vermis. SE induced by PTZ or Li-Pilo statistically significant increased the number of cerebellar BrdU+ cells when compared with the control group (58% and 40%, respectively); maximal cell proliferation occurred in lobules II, III, VIb, VIc, VIII, IXa, and IXb of PTZ-SE group and II, V, VIc, VII, and X of Li-Pilo-SE group. An increased number of BrdU/NeuN+ cells was detected in lobules V (17 ± 1.9), VIc (25.8 ± 2.7), and VII (26.2 ± 3.4) after Li-Pilo-SE compared to their control group (9.8 ± 1.7, 12.8 ± 2.8, and 11 ± 1.7, respectively), while the number of BrdU/NeuN+ cells remained the same after PTZ-induced SE or control conditions. SE induced in the developing rat by different experimental models increases cell proliferation in the granular layer of the cerebellar vermis, but only SE of limbic seizures increases neurogenesis in specific cerebellar lobes.

Changes in multiunit activity pattern in cerebellar cortex associated to olfactory cues during sexual learning in male rats

The cerebellum is a structure of the central nervous system which has been previously studied with different techniques and animal models and even humans, so it is associated with multiple functions such as cognition, memory, emotional processing, balance, control of movement, among others. Its relationship with sensory systems has already been explored, however, the role it plays in olfactory processing in the cerebellum is unclear. Several hypotheses have been proposed from work done in humans and animal models with neuroimaging and immunohistochemical techniques. Everything seems to indicate that the cerebellar function is of vital importance for the olfactory perception, being able to be controlling not only the olfactory aspect, but also the olfactory processing. In this study we analyzed the multiunit activity in the granular layer of the cerebellar vermis during olfactory stimulation: a session being sexually naive and during four sessions of sexual behavior learning. The amplitude was compared between male naive and sexual experts, as well as between olfactory stimuli. The amplitude of the sexually experienced rats showed the highest values compared to naive ones. Odor of receptive female causes the greatest amplitudes, however, in the control group the amplitude increased when they were sexually experts. The motor, sensory and associative learning generated by the acquisition of sexual experience modifies the activation pattern in the cerebellum by presenting neutral odors or associated with a reward.

Role of the androgen receptor in the central nervous system

The involvement of gonadal androgens in functions of the central nervous system was suggested for the first time about half a century ago. Since then, the number of functions attributed to androgens has steadily increased, ranging from regulation of the hypothalamic-pituitary-gonadal axis and reproductive behaviors to modulation of cognition, anxiety and other non-reproductive functions. This review focuses on the implication of the neural androgen receptor in these androgen-sensitive functions and behaviors.

Olfactory stimulation induces cerebellar vermis activation during sexual learning in male rats

The cerebellum is a complex structure mainly recognized for its participation in motor activity and balance, and less understood for its role in olfactory processing. Herein, we assessed Fos immunoreactivity (Fos-IR) in the cerebellar vermis following exposure to different odors during sexual training in male rats. Males were allowed to copulate for either one, three or five sessions. One day after the corresponding session they were exposed during 60 min to woodshaving that was either: clean (Control), sprayed with almond scent (Alm) or from cages of sexually receptive females (RF). The vermis of the cerebellum was removed, cut in sagittal sections and analyzed for Fos-IR to infer activation. Our results showed that the cerebellum responded with more Fos-IR in the Alm and RF groups as compared to Control. More copulatory sessions resulted in more odor-induced Fos-IR, especially in the RF group. Accordingly, we discuss possible mechanisms on how the cerebellum mediates processing of both unconditioned and conditioned odors, and how sexual experience accelerates such process.

Time course of the effect of status epilepticus induced in the developing rat on γ-amino butyric acid and glutamate cerebellar concentration

INTRODUCTION

Status epilepticus (SE) is an epileptic condition that can cause cerebellar atrophy and loss of Purkinje cells in both humans and research animals. Cerebellum is a region rich in γ-aminobutyric acid (GABA) and glutamate, and some studies have shown that their concentrations may be altered after convulsions. However, there are no studies showing the effect of seizures on different cerebellar regions in developing rats. Time course of the effect of status epilepticus induced in the developing rat on γ-amino butyric acid and glutamate cerebellar concentration.

METHODS

SE was induced using the lithium-pilocarpine model; control rats were injected with saline solution. At 6h, 24h, and 1 month after SE o saline injection, rats were anaesthetised with pentobarbital and decapitated, and cerebella were extracted. The vermis and hemispheres were dissected and homogenised in 0.1M perchloric acid containing 4mM sodium bisulfite. Homogenates were centrifuged and supernatant was used to quantify GABA, and glutamate tissue concentrations by HPLC coupled with fluorometric detection.

RESULTS

SE did not alter GABA and glutamate tissue concentration in the cerebellar vermis and hemispheres.

CONCLUSION

The developing rat cerebellum is resistant to both short- and long-term neurochemical changes induced by SE.

The role of orgasm in the development and shaping of partner preferences

BACKGROUND

The effect of orgasm on the development and shaping of partner preferences may involve a catalysis of the neurochemical mechanisms of bonding. Therefore, understanding such process is relevant for neuroscience and psychology.

METHODS

A systematic review was carried out using the terms Orgasm, Sexual Reward, Partner Preference, Pair Bonding, Brain, Learning, Sex, Copulation.

RESULTS

In humans, concentrations of arousing neurotransmitters and potential bonding neurotransmitters increase during orgasm in the cerebrospinal fluid and the bloodstream. Similarly, studies in animals indicate that those neurotransmitters (noradrenaline, oxytocin, prolactin) and others (e.g. dopamine, opioids, serotonin) modulate the appetitive and consummatory phases of sexual behavior and reward. This suggests a link between the experience of orgasm/sexual reward and the neurochemical mechanisms of pair bonding. Orgasm/reward functions as an unconditioned stimulus (UCS). Some areas in the nervous system function as UCS-detection centers, which become activated during orgasm. Partner-related cues function as conditioned stimuli (CS) and are processed in CS-detector centers.

CONCLUSIONS

Throughout the article, we discuss how UCS- and CS-detection centers must interact to facilitate memory consolidation and produce recognition and motivation during future social encounters.

Molecular mechanisms and the conflict between courtship and aggression in three-spined sticklebacks

In nature, animals often face conflicting demands. For example, breeding males must attract a mate but at the same time be ready to defend against rivals. The molecular mechanisms by which the brain resolves behavioural trade-offs are largely unknown. In this study, we compared the brain transcriptional responses of territorial male three-spined sticklebacks to a mating opportunity with a female and to a territorial challenge by a rival male. We focused on the diencephalon and the cerebellum, two regions of the brain implicated in courtship and aggression. There was a set of genes that were differentially expressed in response to both a courtship opportunity and a territorial challenge. Closer inspection of the direction of regulation revealed that genes that were downregulated in response to a courtship opportunity were upregulated in response to a territorial challenge and vice versa. Our study reveals some of the potential molecular mechanisms underlying behavioural trade-offs between sex and aggression, along with a possible solution to the conflict via social context-dependent gene regulation.

Have we been ignoring the elephant in the room? Seven arguments for considering the cerebellum as part of addiction circuitry

Addiction involves alterations in multiple brain regions that are associated with functions such as memory, motivation and executive control. Indeed, it is now well accepted that addictive drugs produce long-lasting molecular and structural plasticity changes in corticostriatal-limbic loops. However, there are brain regions that might be relevant to addiction other than the prefrontal cortex, amygdala, hippocampus and basal ganglia. In addition to these circuits, a growing amount of data suggests the involvement of the cerebellum in many of the brain functions affected in addicts, though this region has been overlooked, traditionally, in the addiction field. Therefore, in the present review we provide seven arguments as to why we should consider the cerebellum in drug addiction. We present and discuss compelling evidence about the effects of drugs of abuse on cerebellar plasticity, the involvement of the cerebellum in drug-induced cue-related memories, and several findings showing that the instrumental memory and executive functions also recruit the cerebellar circuitry. In addition, a hypothetical model of the cerebellum's role relative to other areas within corticostriatal-limbic networks is also provided. Our goal is not to review animal and human studies exhaustively but to support the inclusion of cerebellar alterations as a part of the physiopathology of addiction disorder.

Activation of the cerebellum by olfactory stimulation in sexually naive male rats

INTRODUCTION

The cerebellum has been linked to multiple functions, such as motor control, cognition, memory, and emotional processing. As for its involvement in the sensory systems, the role of the cerebellum in the sense of smell remains unclear. We suggest that sexually naive male rats will present increased neuronal activity in the cerebellar vermis after being stimulated with almond odour or oestrous odour from receptive females.

METHODS

We compared activity in the cerebellar vermis using Fos immunoreactivity after olfactory stimulation. Stimulation took place during 60 min in a cube-shaped acrylic chamber with a double bottom. Stimuli were clean woodchip bedding, bedding with almond extract, and bedding taken from a cage of receptive females. Male rats were subsequently anaesthetised with intraperitoneal sodium pentobarbital. Cerebellar tissue was fixed with paraformaldehyde for later immunohistochemical analysis.

RESULTS

The number of Fos immunoreactive cells in all lobes of the cerebellar vermis was similar between groups stimulated with almond extract and with oestrous odour, and higher than in the clean woodchip group.

CONCLUSIONS

Stimulation of the main olfactory system (almond) and the accessory system (oestrous odour) increases Fos protein production in the granular layer of the cortex of the cerebellar vermis in naive male rats.

Who, what, where, when (and maybe even why)? How the experience of sexual reward connects sexual desire, preference, and performance

Although sexual behavior is controlled by hormonal and neurochemical actions in the brain, sexual experience induces a degree of plasticity that allows animals to form instrumental and Pavlovian associations that predict sexual outcomes, thereby directing the strength of sexual responding. This review describes how experience with sexual reward strengthens the development of sexual behavior and induces sexually-conditioned place and partner preferences in rats. In both male and female rats, early sexual experience with partners scented with a neutral or even noxious odor induces a preference for scented partners in subsequent choice tests. Those preferences can also be induced by injections of morphine or oxytocin paired with a male rat's first exposure to scented females, indicating that pharmacological activation of opioid or oxytocin receptors can "stand in" for the sexual reward-related neurochemical processes normally activated by sexual stimulation. Conversely, conditioned place or partner preferences can be blocked by the opioid receptor antagonist naloxone. A somatosensory cue (a rodent jacket) paired with sexual reward comes to elicit sexual arousal in male rats, such that paired rats with the jacket off show dramatic copulatory deficits. We propose that endogenous opioid activation forms the basis of sexual reward, which also sensitizes hypothalamic and mesolimbic dopamine systems in the presence of cues that predict sexual reward. Those systems act to focus attention on, and activate goal-directed behavior toward, reward-related stimuli. Thus, a critical period exists during an individual's early sexual experience that creates a "love map" or Gestalt of features, movements, feelings, and interpersonal interactions associated with sexual reward.

Modulatory effects of theta burst stimulation on cerebellar nonsomatic functions

Clinical and functional imaging studies suggest that the cerebellar vermis is involved in the regulation of a range of nonsomatic functions including cardiovascular control, thirst, feeding behavior, and primal emotions. Cerebello-hypothalamic circuits have been postulated to be a potential neuroanatomical substrate underlying this modulation. We tested this putative relationship between the cerebellar vermis and nonsomatic functions by stimulating the cerebellum noninvasively via neuronavigated transcranial magnetic stimulation. In this randomized, counter-balanced, within-subject study, intermittent theta burst stimulation (TBS) was applied on three different days to the vermis and the right and left cerebellar hemispheres of 12 right-handed normal subjects with the aim of modulating activity in the targeted cerebellar structure. TBS-associated changes were investigated via cardiovascular monitoring, a series of emotionally arousing picture stimuli, subjective analog scales for primal emotions, and the Profile of Mood States test. All 36 sessions of cerebellar stimulation were tolerated well without serious adverse events. Cardiovascular monitoring pointed to a mild but significant decrease in heart rate subsequent to vermal stimulation; no changes were detected in systolic or diastolic blood pressure measurements. Subjective ratings detected a significant increase in Thirst and a trend toward increased Appetite following vermal stimulation. These observations are consistent with existing neurophysiological and neuroimaging data indicating a role for the cerebellum in the regulation of visceral responses. In conjunction with the modulatory function of the cerebellum, our results suggest a role for the vermis in somatovisceral integration likely through cerebello-hypothalamic pathways. Further research is warranted to elucidate the potential mechanisms underlying the cerebellar modulation of nonsomatic functions.

Multiunit recording of the cerebellar cortex, inferior olive, and fastigial nucleus during copulation in naive and sexually experienced male rats

The sexual behavior of male rats constitutes a natural model to study learning of motor skills at the level of the central nervous system. We previously showed that sexual behavior increases Fos expression in granule cells at lobules 6 to 9 of the vermis cerebellum. Herein, we obtained multiunit recordings of lobules 6a and 7 during the training period of naive subjects, and during consecutive ejaculations of expert males. Recordings from both lobules and the inferior olive showed that the maximum amplitude of mount, intromission, and ejaculation signals were similar, but sexual behavior during training tests produced a decrease in the amplitude for mount and intromission signals. The fastigial nucleus showed an inverse mirror-like response. Thus, the cerebellum is involved in the neural basis of sexual behavior and the learning of appropriate behavioral displays during copulation, with a wiring that involves the cerebellar cortex, inferior olive, and fastigial nucleus.

24-h profiles of direct current brain potential fluctuation in rats

The long-term profile of direct current (DC) brain potential fluctuation has not yet been clarified. In this study, DC potentials were recorded in the frontal area of the cerebral cortex, referenced to the cerebellum, for 24h in freely moving rats under light control (dark period: 20:00-8:00 h). Significant diurnal variation was observed, and the DC potential at the frontal area during the light period was more positive to the cerebellum than during the dark period. Amplitudes of DC potentials were negatively correlated with muscular activity. In addition, phasic negative shifts with durations of less than an hour were observed and were accompanied by muscular activation and delta wave suppression. These results suggest that the DC brain potentials fluctuate during the day and are related to changes in arousal level.